摘要:

AbstractUrea tartrate, CO(NH2)2(+)C4H6O6(hereafter abbraviated as UT) is reported for the first time. Large Single Crystals have been grown by the cooling method from aqueous solution. Some of its physical properties have been measured. The second harmonic generation of powder specimens is about three times larger than that of KH2PO4.

ISSN:0232-1300    

DOI:10.1002/crat.2170310109

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe crystal structure of 6,6′‐dimethoxy‐2,2′‐diphenyl‐19‐crown‐5 Hg(SCN)2has been determined from three‐dimensional X‐ray diffraction data. The compound crystallizes in the triclinic space group P1(no 2) with unit cell parameters α = 9.712(6) Å, β = 11.137(7) Å,c= 14.768(12) Å, α = 86.04(5), β = 80.36(4), γ = 65.70(4),Z= 2,V= 1435(2) Å3. The structure was determined by direct methods which on refinement yielded a fina

ISSN:0232-1300    

DOI:10.1002/crat.2170310110

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractC60· 2C8H10(100 K): hexagonal space group P63,a= 23.694(4),c= 10.046(2) Å,V= 4884(2) Å3,Dx= 1.903 g cm−3,Z= 6,F(000) = 2856, γ(CuKa) = 1.54178 Å, μ = 0.84 mm−1. C60· 2C8H10(20 K): hexagonal space group P63,a= 23.67(1),c= 10.02(1) Å,V= 4862(6) Å3,Dx= 1.912 g cm−3,Z= 6,F(000) = 2856, γ(CuKa) = 1.54178 Å, μ = 0.84 mm−1. The structures were determined by Patterson syntheses and rigid‐body refinements. The C60molecules show two orientations with one molecular centre in common. The solvent molecules are disordered too. Static disorder could not be overcome or influenced by cooling down. A coordination number of 10 was found for th

ISSN:0232-1300    

DOI:10.1002/crat.2170310111

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractTwins and oriented intergrowths are often caused by structural instabilities. A conflict arises between the highest symmetric and the most favourable energetic structural arrangement. A necessary condition for twin growth is the presence of lattice pseudosymmetries. This was shown with two additional examples, maleic acid and 3,5‐dimethylbenzoic acid. Both substances are known practically only as twins. Using lattice‐energy calculations, energetic arrangements that are more favourable were found in both cases. These structures explain the transition that can exist between the twin crystal pa

ISSN:0232-1300    

DOI:10.1002/crat.2170310112

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractOptical absorption spectra in the photon energy range from 0.03 to 1.1 eV and photoreflectance spectra in the range of the fundamental edge are measured on p‐type CuInSe2single crystals. Besides a dominant contribution to the absorption coefficient due to intervalence band transitions below about 0.75 eV the spectra revealed five additional structures that can be ascribed to defect induced optical transitions with characteristic energies between 0.48 and 0.72 eV. Based on a comparison of the near‐edge optical absorption and photoreflectance spectra a shallow defect (donor or acceptor) with an ionisation energy of about 46 meV was identif

ISSN:0232-1300    

DOI:10.1002/crat.2170310113

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractX‐ray excited photoelectron spectroscopy is used to analyse the near‐surface properties of CuInTe2single crystals grown by the vertical Bridgman method. It is found that keeping the crystals at room temperature in air for relatively short times is sufficient for the formation of an oxide layer which consists mainly of TeO2. No detectable amounts of copper or indium oxides could be obser

ISSN:0232-1300    

DOI:10.1002/crat.2170310114

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of polyhalite (K2SO4· MgSO4· 2 CaSO4· 2H2O) was investigated by DSC/TG and X‐ray powder diffraction. The decomposition of the polyhalite starts at 285 °C in releasing the crystal water within one step. Simultaneously the decomposition of the polyhalite into anhydrite and two solid solutions of the compositions K2SO4· 1.76 MgSO4· 0.24 CaSO4and K2SO4· 0.64 MgSO4· 1.36 CaSO4is taking place. The mechanism of decomposition runs through K2SO4· MgSO4CaSO4. This phase reacts immediately to the solid solutions, menti

ISSN:0232-1300    

DOI:10.1002/crat.2170310115

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThermal decomposition of freeze‐dried complex oxalate precursors allows the synthesis of crystalline phases in the FeNbO4TiO2system at relatively low temperature. This system shows not only a rutiletype, but also a wolframite‐type solid solution (ss), which exists at lower temperatures. The temperature of the reversible transformation wolframite‐rutile decreases with increasing TiO2

ISSN:0232-1300    

DOI:10.1002/crat.2170310116

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe systems Cd(C6H5COO)2CdCl2H2O and Cd(C6H5COO)2CdBr2H2O have been studied at 25 °C. Formation of the double salts Cd(C6H5COO)2· CdCl2and Cd(C6H5COO)2· CdBr2(1:1:0) has been established and their chemical individuality has been confirmed by chemical, X‐ray, and DT‐analyses.Proceeding from data on the structure of Cd(C6H5COO)2· 2 H2O and the composition of the 1:1:0 double salts as well as using Pauling's rules for the most probable spacial disposition of the ions, the crystal structure type of the double salts obtaine

ISSN:0232-1300    

DOI:10.1002/crat.2170310117

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe crystal structure as well as the temperature and composition dependences of the lattice parameters, the thermal expansion coefficients in the high‐temperature superconducting Ba1–xBiO3system were determined by an X‐ray powder diffraction method at temperatures between 80 and 650 K. The character of variation of intensity, profiles, and line widths of the diffraction lines for different perovskite structures as a function of the contentxand temperatures was found. The correlation between the behaviour of the thermal expansion coefficients and potassium content was revealed at different temperatures. It is shown that the thermal expansion coefficients vary inversely with risingxat any temperature in the range from 80 to

ISSN:0232-1300    

DOI:10.1002/crat.2170310118

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY